The textbook values you get from basic crossover design tools assume a lot of things, they assume they are connected to a driver with a perfect 'x' ohm load with no inductive impedance rice, no resonant peaks and perfectly flat phase and frequency response. In reality this isn't the case and overcoming these effects is all part of the art of designing a good speaker.

To do it properly you do need some measurement equipment, you can get reasonably good results by ear but not to the full potential of the components used.